1. Field of the Invention
The invention concerns a medical system architecture to transfer and represent image data of medical multi-component images, of the type having at least one modality to acquire examination images; computer workstations associated with the respective modalities to process the examination images; a device to transfer the examination images; a device for storage of data and the examination images; and with further user workstations for post-processing the examination images. The invention also concerns a method to operate such a medical system architecture.
2. Description of the Prior Art
Known from the book “Bildgebende Systeme für die medizinische Diagnostik”, published by H. Morneburg, 3rd edition, 1995, pages 684 et seq. are medical system architectures, known as PACS (Picture Archival and Communication Systems), in which the images generated by modalities are stored in an image storage system or image archival system. Image viewing and image processing stations, known as workstations, are connected with one another via an image communication network to retrieve patient and image data.
Large image data sets are transferred and visualized in such medical system architectures, but often only a comparatively small transfer bandwidth is available.
The image data can be individual images, image series or volume datasets. Individual images that presently can be only transferred slowly are, for example, mammography images. An image series or multi-component images include, among other things, a set of individual images, known as image components, or simply components that have references to one another. Furthermore, in addition to the images, a multi-component image can include non-image information, for example ECG signals. The multi-component images can be, for example, CT slices the position of which can be established along the z-axis (the direction of the spiral track). Naturally, multi-component images can be generated not only with CT, but also with other modalities (for example by magnetic resonance techniques). Even volumes, as are acquired in 3D rotation angiography, can be considered as multi component images, as can image sequences that result from heart examinations. In the first case, the data exist in a common spatial coordinate system. In the second case, there are two spatial axes and one time axis that are common to all individual components.
To control interactive transfer of compressed multi-component data, parameters can be used that are freely adjustable within specific intervals. For example, compressed image data can be transferred with which, after receipt and decompression, an image sub-region (ROI) results with a selected resolution with required image quality. During the data transmission, however, an image display is already possible by which, for example, an image can be initially displayed at a lower resolution level with lower quality. As soon as more data are present, it then changes over to higher resolutions with better quality. This visualization procedure is designated as a progressive image representation.
Current image data compression methods such as JPEG-2000 or Motion JPEG-2000 are able to represent compressed individual image data and components of color images in a packet-based manner. Color images are, for example, spectral multi-component images in which all components are normally represented together as a color image. By targeted transfer of packets. JPEG-2000 offers the possibility to control the resolution, the section and the image quality of individual (color) images. The standardized JPEG-2000 (part 1) already offers important specifications for transfer of compressed image data and their progressive, multiple-resolution display. Packets can be generated with JPEG-2000 during the image data compression, with the compressed image data contents being described by the four parameters of image resolution (A), quality (Q), component index (K) and position in the image (ROI). JPEG-2000 also is able to write these data in a form known as a “codestream” that allows access to individual packets, however, part 1 only provides multi-component transformations in color images. This part of the standard therefore offers no possibility to generate individual components of a (medical) multi-component image with variable slice thickness. If it is desired to employ JPEG-2000, however, components could be generated using part 3 (Motion JPEG-2000), with variable slice thickness, by three gray components being considered as color components of an individual image and, for example, a reversible code transformation (RCT) being implemented. A “mean component” and two difference components are thereby obtained. The JPEG standard is described, for example, by Skodras et al. in “The JPEG 2000 Still Image Compression Standard”, IEEE Signal Processing Magazine, pages 36 through 58, September 2001.
In additional to part 1, JPEG-2000 also provides, among other things, as part 10 (JP3D), the standardization process of which still is not completed. At present work is underway for finalizing this part of the JPEG-2000 standard and to create a reference implementation (known as a VM). A substantial difference of JP3D from the conventional JPEG-2000 approach may be that, in JP3D, a 3-D wavelet transformation will be provided to separate a volume that can ensue recursively along all three spatial directions. After the calculation of the wavelet transformation, the coefficients will be split into so-called “code blocks” (or “code cubes”) and coded.
Designs also are available for the interactive transmission of image data that have been compressed with JPEG-2000. An interactive transfer of data packets of an image is already possible with the JPIP (JPEG-2000 Internet Protocol) discussed in this context.
The previous variants of JPIP, however, exhibit shortcomings. JPIP only makes available an incomplete set of metadate. Thus, the client is not able to determine, for example, the status of a specific received packet, since the “Unique Data Bin Identifier” used in JPIP provides no such information. With JPIP, this can possibly result in individual components of a large multi-component image being displayed with a different quality from the rest. This problem ensues particularly given large slice image data sets and slow data rates, for which a comparably long time can be required until consistent data for all slice images have been received. The calculation and rendering of large multi-component images also occupies a not-inconsiderable time. Therefore it is attempted to show images only at chosen points in time, in order to avoid visualization difficulties.
From the article by the company Merge Technologies Inc., “Image Channel™ White Paper” of 22 Apr. '02, a transfer system is known with which images, for example of a study, can be transferred from a server to a client with a specified resolution with progressive quality, as long as the images exist in JPEG-2000. Furthermore, the possibility exists to select ROIs using a low-resolution complete image. In this manner, corresponding data can be requested compressed that can then (after receipt and decompression) be shown in the highest resolution. Merge, as a producer of PACS software, assumes that the images are present in the DICOM format, however, only JPEG-2000 individual images exist in DICOM at present. Multi-component images with a number of individual slices that exist in the JPEG-2000 format are currently still not DICOM-compatible.